The disclosure pertains to a process to manufacture a spun-dyed para-aramid filament yarn and a sliver, a sliver, a staple fiber yarn and a textile fabric.
Spun-dyed para-aramid filament yarns are known. To achieve a deeper colour of the spun-dyed filament yarn the concentration of dyestuff in the filament yarn can be increased. However, increasing the concentration of dye in the para-aramid filament yarn increases the tendency of the filament yarn to form intermittent defects in the filaments which extend along the center of the filament fiber axis and exhibit a cylinder-like shape. Said defects can be detected with a microscope at a magnification factor of 50 using visible light.
It was found that, if spun dyed para-aramid filament yarns with said tendency of defect formation are used to manufacture a sliver, the obtained sliver exhibits neps. According to the definition given in C. A. Lawrence in “Fundamentals of Spun Yarn Technology” a nep is a small, tangled knot of fiber often caused by processing fibers.
And it was found that said formation of neps causes fading of the colour of the dye, so that the colour of the sliver is faded in comparison with the colour of the spun-dyed para-aramid filament yarn which was used to manufacture the sliver. Said colour fading of the sliver is especially pronounced, if the sliver is made from stretch-broken staple fibers, but can also be detected, even though less pronounced, in a sliver made from cut staple fibers. If such colour-faded sliver is manufactured into a staple fiber yarn, it was observed that the resulting staple fiber yarn exhibits increased nep formation and correspondingly increased colour fading. And, of course, both nep formation and colour fading are transferred into a textile fabric made from said staple fiber yarn.
Therefore, the problem of the present disclosure is to provide a process resulting in a spun-dyed para-aramid filament yarn which also at an increased concentration of the dye in the filament yarn is at least less susceptible to form the defects described above, and which can be used to manufacture a sliver, a staple fiber yarn from said sliver, and textile fabrics from said staple fiber yarn exhibiting less nep formation and colour-fading.